mac80211: make noack test available

There's this internal wifi_wme_noack_test variable that
we use to set the QoS control if set. For one, it is
unlikely that it is set. Secondly, if set it needs to
influence the IEEE80211_TX_CTL_NO_ACK TX control flag,
and finally we should also be able to set it at all, so
make it available in debugfs.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/wme.c b/net/mac80211/wme.c
index 0b8ad1f4..45b74f3 100644
--- a/net/mac80211/wme.c
+++ b/net/mac80211/wme.c
@@ -133,7 +133,7 @@
 		u8 *p = ieee80211_get_qos_ctl(hdr);
 		u8 ack_policy = 0;
 		tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;
-		if (local->wifi_wme_noack_test)
+		if (unlikely(local->wifi_wme_noack_test))
 			ack_policy |= QOS_CONTROL_ACK_POLICY_NOACK <<
 					QOS_CONTROL_ACK_POLICY_SHIFT;
 		/* qos header is 2 bytes, second reserved */